Introduction
　　Recent trials have demonstrated the superior efficacy of mechanical thrombectomy over other medical treatments for acute ischemic stroke. However, not every large vessel occlusion (LVO) can be recanalized using a single thrombectomy device. Rescue devices were proved to increase the reperfusion rate, but the efficacy is unclear.
Objective:
　　In this study, we evaluated the efficacy of rescue therapy and compared different thrombectomy techniques in different location of LVO.
Methods
　　We analyzed the outcomes of mechanical thrombectomy from a prospective registry of consecutive 82 patients in Taipei Medical University Hospital. The reperfusion rate and the functional outcome were compared in patients who received first-line therapy only and patients who need rescue therapy.
Results
　　An 84.1% reperfusion rate was achieved in our cohort. We applied first-line stent retriever (SR) treatment in 6 patients, among which 4 (66.6%) achieved successful reperfusion. We applied a direct-aspiration first-pass technique (ADAPT) as the first-line treatment in 76 patients, among which 46 (60.5%) achieved successful reperfusion. Successful reperfusion could not be achieved in 30 cases (39.5%); therefore, we applied a second-line rescue SR for 28 patients, and reperfusion was established in 18 (64.3%) of them. Our result revealed that the LVO in anterior circulation has higher chance to response to SR rescue therapy than posterior circulation lesions (68.0% vs 33.3%, P < .001). Patients who received first-line therapy only exhibited significantly better functional outcomes than those who also treated with rescue SR therapy (41.2% vs 16.7%, P=.001). Moreover, patients with LVO in the anterior circulation were found to have a higher probability of achieving functional independence than patients with posterior circulation lesion (10.7% vs 0.0%, P < .001). Conclusion Our study reveals that rescue SR therapy improves reperfusion rate. Patients who require rescue SR therapy have a lower likelihood of functional independence. LVO in the anterior circulation responds better to rescue SR therapy than posterior circulation lesions.